Our present knowledge of how the sciatic nerve attemps to regenerate after injury is very limited. How the neuron is instructed to begin to regenerate and what kind of information originates from the environment close to the injury are important experimental questions that need to be addressed. We have constructed cDNA libraries of the dorsal root ganglia and sciatic nerve three days after nerve crush. The screening of these libraries has resulted in the isolation of cDNA clones that were either repressed or induced during the regeneration process. We have concentrated our effort to study and characterize the response of two cDNAs named SR13 and D112 are full length cDNA clones that were isolated from a sciatic nerve cDNA library. The SR13 cDNA codes a protein that may play an important role in the proliferation of Schwann cells that results during nerve regeneration in the segment distal to a crush or cut and D112 is the human FK506 binding protein. The understanding of how these clones are differentially regulated may provide us with the necessary tools to understand the regeneration process and the role of their protein product in the cell.